Actually, that sounds like it could be the random offset in the meter itself - this is mandatory and I’m afraid OVO can’t modify it.

Sending ECAUL might fix things a bit, but that’s about it.

What does your meter look like @davidlawman ? Does it have 5 cables connected ? Post a photo if you can. 
Usually with these meters, the off peak circuit is switched by the extra cable and so whenever this switches (can be offset as Blastoise mentions), during that whole time you get off peak charges so even if it switches on later you get off peak till it switches off later too

How did you find this out?

As the other respondents have said, there is a random delay built in to the meter which is supposed to apply to both tariff changes and load switching. If your E7 tariff is nominally changing at, say, midnight, it will in fact change a few minutes - up to 30 - later. If the meter is properly configured, the control which switches your heating appliances on and off should follow precisely the same timings. 

Depending on the meter (which is why BPLightlog asked for a photo of it), it should be possible to see on its display what the tariff is at any particular time, which register the current usage is being recorded on and whether the heating circuits are active or not at the time. If as you say there’s a delay in the tariff and register switch but not in the load control, it should be obvious from the meter display a few minutes after a scheduled switch, e.g. at 07:10 if your offpeak period nominally ends at 07:00. A photo of the display at this time showing the current register and tariff should reveal all.  

I quite understand about the random offset but surely I should still get seven hours at the cheap rate. Surely when the cheap rate is applied, whether it is midnight or any point in the next half hour, the power should be applied at the same time and switch off seven hours later when it reverts to day rate.

What is actually happening is at exactly midnight the In-house display and the smart meter both switch to display the E7 rate (approx. 21 pence per hour)  but the E7 power is not switched on until exactly thirty minutes later. Six and a half hours after the power was switched at exactly seven am the rate displayed on the smart meter and the in-house display revert to the day rate (approx. 31 pence per unit). Now the problem is, My E7 appliances, water heaters and storage heaters do not switch off until seven-thirty so I’m being charged at the expensive rate for 30 minutes.

The meter has five cables. It is a Toshiba Aclara SGM1416-b.

Thanks to everyone for the replies.

Dave

Thanks for the photo @davidlawman , with the fifth terminal being switched to power off peak it has its own separate register (recording).

What this means is that although your IHD might show the switch differently, the totals which log your peak and off peak use will line up with the timed ‘window’ and so even though it’s not exactly on the hour, you’ll still get the full time period at the proper rates. 
Only the meter is used for billing, not the IHD so those rate registers are the ones used and they are active (and not) when the fifth terminal switches

Thanks for your reply BPLightlog. I’ll assume all is OK then. I can see the E7 circuit is active for the full 7 hours but I’m not finding the meter very user friendly if it is displaying the wrong rate between 7:00am and 7:30am.

Best wishes

Dave

Yes the in house display (IHD) isn’t very helpful in this situation. 
On your meter, you can see when the meter switches by the display in the bottom right hand corner. (Labelled 1 and 2)

Thanks for the photo.  It would be really helpful if we could see the actual display on the meter. BP’s image illustrates the amount of detail available from it.

Does it really take seven hours to charge up your storage heaters and heat up the water tank? They are usually thermostatically-controlled, so once they’re fully charged, they stop drawing power even though the circuit may still be active. 

For example, it takes about 10 kWh to heat my 200l water tank to 55ºC. If the lower element in the tank is 3kW, switched on at 00:30, the thermostat would turn it off before 04:00. It’s not particularly well insulated, but even so I don’t notice it heating up again that night. Similarly with the storage heaters. It would be an unusual system that was still using heating power between 07:00 and 07:30. 

As BP points out, you can’t rely on the IHD to indicate when the tariff changes. It picks up the calendar from the meter, but it’s probably not aware of the offset, so it will show the offpeak tariff from its nominal start time, even though this tariff doesn’t take effect until the end of the offset.

You can rely on it, though, to warn you when the heating circuits are active and running: the ‘using now’ figure will be several kW, not less than 1kW as it probably would be before they come on. If this is what you’re seeing at 07:10, the meter may need an adjustment. 

Hi Firedog, Thanks for your reply. Sorry I didn’t get the display on the photograph. The sun was shining on the meter. My water heater is very well insulated so no problem there but the storage heaters do tend to click in and out occasionally during the night after they reach temperature. They use around 11 units per night each. 

Dave